The proposed work deals with the effect of gram negative endotoxin on murine lymphoid cells and macrophages. The hypothesis is that binding of LPS to the B lymphocyte cell membrane triggers its mitogenic effect. Consequently, we intend to quantitate binding of LPS to B and T cells, measure the affinity of binding and correlate the binding of LPS with the extent of stimulation. We will also look for endocytosis of LPS by lymphoid cells. LPS appears to have cytotoxic and stimulatory effects on macrophages, and some of the biological effects of LPS may be mediated via macrophages. We will study the morphological, biochemical, and functional changes in normal and in induced macrophages from normal mice, hyperreactive mice, cortisone protected mice, and LPS tolerant mice. These data will help clarify the effect of LPS on these cells and will help determine if the role of these cells as mediators of LPS effects is possible and probable. BIBLIOGRAPHIC REFERENCES: Gormus, B.J. and J.W. Shands, Jr. Capping of the lymphocyte C receptor and temperature dependent loss of C3 rosettes. J. Immunol. 114: 1221, 1975. Gormus, B.J. and J.W. Shands, Jr. Endotoxin stimulated spleen cells: characterization of the responding cells. J. Immunol. 115: 118, 1975.